Prominent and Persistent Extraneural Infection in Human PrP Transgenic Mice Infected with Variant CJD

Background. The evolution of the variant Creutzfeldt-Jakob disease (vCJD) epidemic is hazardous to predict due to uncertainty in ascertaining the prevalence of infection and because the disease might remain asymptomatic or produce an alternate, sporadic-like phenotype. Methodology/Principal Findings. Transgenic mice were produced that overexpress human prion protein with methionine at codon 129, the only allele found so far in vCJD-affected patients. These mice were infected with prions derived from variant and sporadic CJD (sCJD) cases by intracerebral or intraperitoneal route, and transmission efficiency and strain phenotype were analyzed in brain and spleen. We showed that i) the main features of vCJD infection in humans, including a prominent involvement of the lymphoid tissues compared to that in sCJD infection were faithfully reproduced in such mice; ii) transmission of vCJD agent by intracerebral route could lead to the propagation of either vCJD or sCJD-like prion in the brain, whereas vCJD prion was invariably propagated in the spleen, iii) after peripheral exposure, inefficient neuroinvasion was observed, resulting in an asymptomatic infection with life-long persistence of vCJD prion in the spleen at stable and elevated levels. Conclusion/Significance. Our findings emphasize the possibility that human-to-human transmission of vCJD might produce alternative neuropathogical phenotypes and that lymphoid tissue examination of CJD cases classified as sporadic might reveal an infection by vCJD-type prions. They also provide evidence for the strong propensity of this agent to establish long-lasting, subclinical vCJD infection of lymphoreticular tissues, thus amplifying the risk for iatrogenic transmission

The Physical Relationship between Infectivity and Prion Protein Aggregates Is Strain-Dependent

Prions are unconventional infectious agents thought to be primarily composed of PrPSc, a multimeric misfolded conformer of the ubiquitously expressed host-encoded prion protein (PrPC). They cause fatal neurodegenerative diseases in both animals and humans. The disease phenotype is not uniform within species, and stable, self-propagating variations in PrPSc conformation could encode this ‘strain’ diversity. However, much remains to be learned about the physical relationship between the infectious agent and PrPSc aggregation state, and how this varies according to the strain. We applied a sedimentation velocity technique to a panel of natural, biologically cloned strains obtained by propagation of classical and atypical sheep scrapie and BSE infectious sources in transgenic mice expressing ovine PrP. Detergent-solubilized, infected brain homogenates were used as starting material. Solubilization conditions were optimized to separate PrPSc aggregates from PrPC. The distribution of PrPSc and infectivity in the gradient was determined by immunoblotting and mouse bioassay, respectively. As a general feature, a major proteinase K-resistant PrPSc peak was observed in the middle part of the gradient. This population approximately corresponds to multimers of 12–30 PrP molecules, if constituted of PrP only. For two strains, infectivity peaked in a markedly different region of the gradient. This most infectious component sedimented very slowly, suggesting small size oligomers and/or low density PrPSc aggregates. Extending this study to hamster prions passaged in hamster PrP transgenic mice revealed that the highly infectious, slowly sedimenting particles could be a feature of strains able to induce a rapidly lethal disease. Our findings suggest that prion infectious particles are subjected to marked strain-dependent variations, which in turn could influence the strain biological phenotype, in particular the replication dynamics

Etude de la diversité et du déterminisme des souches de prion (approches physico-chimiques et analyse comparée)

Les maladies à prions regroupent un ensemble d atteintes neurodégénératives fatales affectant l homme et l animal. Il est aujourd hui communément admis que la protéine prion pathologique (PrPSc) constitue le principal, sinon le seul composant de l agent infectieux prion. La propagation des prions s effectuerait selon un processus de conversion auto-propagé de la protéine prion normale (PrPC) endogène en conformère infectieux PrPSc qui s accumule sous forme d agrégats dans le cerveau des individus atteints. Bien que virtuellement dépourvus de génome, les prions peuvent manifester une diversité de souches phénotypiquement distinctes au sein d une même espèce. Le déterminisme moléculaire de cette diversité qui reposerait sur l existence de conformations différentes de PrPSc, reste très peu documenté. Par l utilisation d une méthodologie fondée sur la sédimentation en vélocité et des approches physico-chimiques, le projet de thèse visait à étudier la diversité conformationnelle des molécules de PrPSc, à décrire leur état de multimérisation en relation avec leur niveau d infectiosité, afin de susciter des éléments de réponse sur le déterminisme du phénotype de la maladie. Les principaux résultats obtenus montrent que l état d agrégation de la PrPSc, la taille des particules infectieuses et la relation entre ces deux entités peuvent notablement varier en fonction de la souche considérée. Les données acquises suggèrent ainsi que la nature des particules infectieuses varie fortement en fonction des souches, influençant en retour le phénotype biologique de souche, en particulier la dynamique de réplicationPrion diseases are a group of neurodegenerative disorders affecting both humans and animals. Prion, the etiologic agent of these diseases is thought to be essentially composed of multimers of an abnormal conformer (PrPSc) of the cellular, monomeric prion protein. Prion propagation is believed to stem from the ability of PrPSc to convert the cellular prion protein (PrPC) into an infectious conformer PrPSc. Biologically distinct prion strain can propagate in the same host, presumably through the self-perpetuation of different, specific PrPSc conformers. However much remains to be known about the physical relationship between the infectious agent and PrPSc conformations, in particular the aggregation state, and to which extent it varies according to the strain. The aim of the thesis was to study the strain-dependant physical diversity of PrPSc molecules, to describe their multimerisation state in relation with infectivity, in order to provide information about the determinism of the disease phenotype. We applied a methodology based on sedimentation velocity and physico-chemicals techniques to a panel of natural, biologically cloned prion strains. The main results suggest that prion infectious particles are subjected to marked strain-dependent variations in aggregation state, which in turn could influence the strain biological phenotype, in particular the replication kinetics.VERSAILLES-BU Sciences et IUT (786462101) / SudocSudocFranceF

Experimental Measurement and Numerical Simulation of the Screening Current-Induced Field Decay in a Small ReBCO Coil

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Investigation on Two Techniques for the Reduction of Screening Current-Induced Field Effects in REBCO HTS Coils

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Automatisation de l'analyse des images et du traitement des données produites à l'aide des logiciels ImageJ et Excel ®

International audienceNous décrivons l'utilisation combinée des logiciels Image J et Excel pour une analyse simple et rapide de plusieurs dizaines de photos afin d'obtenir un tableau final compilant tous les résultats chiffrés. Cette méthode permet d'automatiser, de standardiser des analyses sur plusieurs photos et d'en extraire des données numériques qui donneront des résultats objectifs et précis. Cette technique est modifiable pour une application à différentes études qui nécessitent l'analyse quantitative et qualitative d'images

Experimental measurements of contact resistivity between superconducting HTS tapes with or without metallic co-wound tape

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PrPSc accumulation and stability in ovine PrP transgenic mice infected with biologically distinct scrapie strains

International audienceWhile multiple conformations of the abnormal prion protein (PrPSc) are thought to encipher prion strain diversity, how they feature in the variable incubation periods observed upon experimental transmission into mice is currently unknown. In order to investigate the natural diversity of sheep scrapie agent, our laboratory has developed a new experimental model consisting of transgenic mice overexpressing the VRQ allele of sheep prion protein (tg338 line). Among 6 potential groups of natural scrapie strains, we have presently stabilised 4 strains that have been biologically cloned and shown to produce stable and distinct phenotypes, based on the incubation time (from 60 to ∼200 days), the molecular profile of PrPSc and its regional distribution in the brain. Moreover these scrapie strains differ in their capacity to replicate in peripheral tissues, such as spleen. For each of these strains, we have examined i) the kinetics of PrPSc accumulation in both brain and spleen, ii) the sensitivity of PrPSc to degradation by either digesting the protein with proteinase K or pepsin in an vitro assay or in vivo by exposing brain homogenates containing PrPP Sc to primary cultures of macrophages, iii) the resistance to denaturation with increasing concentration of guanidine-HCl. These data will be presented and their possible significance in term of strain biology will be discussed

Propagation of α-Synuclein Strains within Human Reconstructed Neuronal Network

International audienceReappraisal of neuropathological studies suggests that pathological hallmarks of Alzheimer’s disease and Parkinson’s disease (PD) spread progressively along predictable neuronal pathways in the human brain through unknown mechanisms. Although there is much evidence supporting the prion-like propagation and amplification of α-synuclein (α-Syn) in vitro and in rodent models, whether this scenario occurs in the human brain remains to be substantiated. Here we reconstructed in microfluidic devices corticocortical neuronal networks using human induced pluripotent stem cells derived from a healthy donor. We provide unique experimental evidence that different strains of human α-Syn disseminate in “wild-type” human neuronal networks in a prion-like manner. We show that two distinct α-Syn strains we named fibrils and ribbons are transported, traffic between neurons, and trigger to different extents, in a dose- and structure-dependent manner, the progressive accumulation of PD-like pathological hallmarks. We further demonstrate that seeded aggregation of endogenous soluble α-Syn affects synaptic integrity and mitochondria morphology

Development of a REBCO Insert for a 30 T+ All-Superconducting User Magnet

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